The game that started it all!
Call of Duty is a first-person shooter video game developed by Infinity Ward and published by Activision in 2003. The game simulates the infantry and combined arms warfare of World War II. The game is based on the Quake III: Team Arena engine. It was accompanied in September 2004 by an expansion pack, Call of Duty: United Offensive, which was produced by Activision, and developed by Gray Matter Interactive, with contributions from Pi Studios. Call of Duty is similar in theme and gameplay to Medal of Honor, as it is made out of single-player campaigns and missions. However, unlike Medal of Honor, the war is seen not just from the viewpoint of an American soldier but also from the viewpoint of British and Soviet soldiers.
The game was somewhat unusual at the time in that throughout the single-player mode the player is joined by computer-controlled allies who range in quantity from two infantrymen (in some of the British missions) to an entire regiment of tanks (in the Soviet missions). The computer-controlled allies will support the actual player during the missions. They also further the game's goal of providing an immersive and realistic experience; that is, soldiers in World War II were usually part of a larger group, as opposed to the "lone wolf" seen in video games such as Medal of Honor. However, there are some missions where the player is alone.
As a first-person shooter, Call of Duty places the player in control of an infantry soldier who makes use of various authentic World War II firearms in combat. Each mission features a series of objectives which are marked on the heads-up display's compass; the player must complete all objectives to advance to the next mission. The player can save and load at any time, rather than the checkpoint system utilized in later Call of Duty games.
The player has two primary weapon slots, a handgun slot and can carry up to ten grenades (all of the later Call of Duty games feature only two weapon slots; a sidearm will fill one of these slots). Weapons may be exchanged with those found on the battlefield dropped by dead soldiers. Call of Duty was one of the early first-person shooters to feature iron sights in game play; by pressing the corresponding key the player aims down the actual sights on the gun for increased accuracy. In addition to weapons carried by the player, mounted machine guns and other fixed weapon emplacements are controllable by the player.
The game uses a standard health points system, with a limited amount of health reflected by a health bar. Medkits scattered throughout the levels or dropped by some foes are used to restore health when the player is injured. This contrasts with all subsequent Call of Duty games in which there is no health bar and the player's health recharges when not taking fire.
Call of Duty also featured "shellshock": when there is an explosion near the player, he momentarily experiences simulated tinnitus, appropriate sound "muffling" effects, blurred vision, and also results in the player slowing down, unable to sprint.
As the focus of the game is on simulation of the actual battlefield, the gameplay differs from many single-player shooters of the time. The player moves in conjunction with allied soldiers rather than alone; allied soldiers will assist the player in defeating enemy soldiers and advancing but the player is given charge of completing certain objectives. The game places heavy emphasis on usage of cover, suppressive fire, and grenades. AI-controlled soldiers will take cover behind walls, barricades, and other obstacles when available.